Effects of soil textures and emitter material on the soil water movement and efficiency of negatively pressurized irrigation system

Negatively pressurized irrigation(NPI) method, a newly irrigation technology, in which the elevation of the emitters is higher than that of the water source, runs under negative hydraulic head. The emitter materials and soil textures are important factors in the water movements in soils and the flux of NPI system. A series laboratory experiments were arranged to study the effects of the two factors on the NPI with emitters 0.5 m above the water source. Fibrous emitters and ceramic emitters were used in the experiments as water application emitters to investigate the water movements in a clay loamy soil and a sandy loam. The results show that the relationships between time and cumulative infiltration, the maximum horizontal and vertical wetted distances are power functions, but the values of the clay loamy soil are bigger than those of the sandy loam during the same period with the same emitter. The wetting fronts are almost ellipsoid-shaped. The ratio of the maximum wetted distance in the horizontal to that in the vertical direction in the clay loamy soil, is bigger than that in the sand loam. The flux of NPI system with fibrous emitters is higher than that with ceramic emitters under the same soil texture. The results are useful for selecting emitters for the design and determining the application range of NPI system.